This study examined longitudinal changes in basal ganglia volumes (using MRI) and regional cerebral blood flow (using SPECT) in asymptomatic persons with and without the Huntington's disease genetic mutation. We studied 25 HD mutation-carriers and 29 non-carriers. Among the mutation carriers, there have been 21 Year-2 follow-up scans; 15 Year-3 follow-up scans; 9 Year-4 follow-up scans; and 5 Year-5 follow-up scans. Year-3 follow-up scans have been completed on 19 non-carriers. Concurrent with the scans, we obtained neuropsychological, neurological, and psychosocial data on each person. For our initial analyses, we estimated years-to-onset in mutation carriers and evaluated its relationship to changes in imaging measures. Putamen volume, caudate volume and bicaudate ratio were significantly reduced in carriers 6 or fewer years from onset. Blood flow measurements were less affected by genet status or years-to-onset. The results suggest that quantitative assessment of basal ganglia volume may provide a marker for presymptomatic Huntington's disease. A manuscript, entitled "Reduced basal ganglia blood flow and volume in presymptomatic, gene-tested persons at risk for Huntington's disease," is in press in Brain. Additional analyses are underway.